Some of the keys in the QWERTY line of my keyboard are malfunctioning. Is this a simple hardware fault or is there something else going on?

The keyboard on my trusty MacBook Pro has started playing up. At first the 'i' and 't' keys wouldn't respond properly - they only worked if I held the key down or pressed repeatedly - but now it seems to be spreading to the rest of the QWERTY row, 'o' being the next one to go.

This is probably a simple hardware failure, in which case I'm resigned to a visit to an Apple Store, but if anyone has any other clues/suggestions I'd be very grateful.

It's a 15" 2012 model.

Thanks.